You already have a precision voltage source in your analog keyboard or MIDI to CV
converter.
The purpose of the calibrated input is so we can read an analog keyboard input.
5.000 volts would be 5 octaves of keys and we can read each key by it's key voltage.
That way you can play the keyboard into a sequencer, or use it to transpose sequences.
I'm sure there are other applications. You can also read a keyboad directly via MIDI of
course.
With a 5 volt range, each count is ~5 millivolts, a semitone is 0.083 volts, so there are
around 16 counts between semitones.
Assuming bottom C is zero volts. If your keyboard is only 4 octaves then calibrate at 4.000
volts.
It is not so important that it be absolute real world voltage, but it is nice.
--- In ComputerVoltageSources@yahoogroups.com, "John Loffink" <jloffink@...> wrote:
>
> I think you're on the right track. Use a voltage reference chip, not your
> power supply. Feed this to a high accuracy low voltage offset differential
> amplifier with high gain. Your + and - input resistors are the ones to be
> matched. If both are attached to the voltage reference then the output is
> only the difference between the two and the op amp offsets.
>
> John Loffink
> The Microtonal Synthesis Web Site
> http://www.microtonal-synthesis.com
> The Wavemakers Synthesizer Web Site
> http://www.wavemakers-synth.com
>
>
> > -----Original Message-----
> > From: ComputerVoltageSources@yahoogroups.com
> > [mailto:ComputerVoltageSources@yahoogroups.com] On Behalf Of John Mahoney
> > Sent: Friday, March 24, 2006 8:03 PM
> > To: ComputerVoltageSources@yahoogroups.com
> > Subject: [ComputerVoltageSources] resistor matching, was RE: Calibrated
> > Inputs
> >
> > Re: matching resistors, will the following procedure work?
> >
> > Ingredients:
> > 1 precision voltage reference
> > 1 amplifier
> > 1 voltmeter
> > Resistors to be matched (RTBM)
> >
> > Feed a small, precisely regulated signal through a voltage divider
> > made from an RTBM and some other resistor (the "constant"). Feed the
> > divider's output through the amplifier. Measure the output. Repeat as
> > needed.
> >
> > The idea, obviously, is to amplify the differences between the RTBM
> > so that the voltmeter can register those differences. Concerns would
> > include temperature stability, power supply stability, etc...
> >
> > So, this may not be good enough for a NASA guidance system, but will
> > it suffice for this DIY project? As John Lofflink said, we need only
> > be concerned with relative accuracy.
> > --
> > john
> >
> >
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
>